irradiance.py updates: glossary term links and units (#2311)

* Update irradiance.py

* ongoing...

* ongoing...

* fix . + [ ]

* Update pvlib/irradiance.py

Co-authored-by: Adam R. Jensen <39184289+AdamRJensen@users.noreply.github.com>

* in decimal degrees -> [°]

* reinsert .

* Update irradiance.py

* linter

* Update irradiance.py

* remove unintended 'optional'  for solar_zenith

* add ghi

* Update irradiance.py

* more untis

* Update irradiance.py

* units (add+order)

* Update v0.13.1.rst

* Apply suggestions from code review

Co-authored-by: Cliff Hansen <cwhanse@sandia.gov>

* reformat kt

* linting

* remove SRRL 0.82 comment

* Update v0.13.1.rst

* Apply suggestions from code review

Co-authored-by: Cliff Hansen <cwhanse@sandia.gov>

* linting

* Update irradiance.py

* linting

* Update irradiance.py

---------

Co-authored-by: Adam R. Jensen <39184289+AdamRJensen@users.noreply.github.com>
Co-authored-by: Cliff Hansen <cwhanse@sandia.gov>

Author: 3 people

docs/sphinx/source/whatsnew/v0.13.1.rst

@@ -36,6 +36,10 @@ Enhancements
 
 Documentation
 ~~~~~~~~~~~~~
+* Update :py:mod:`pvlib.irradiance` module documentation to include links to 
+  parameter definitions from the nomenclature page, ensure consistent
+  parameter description structure, add units to all parameters where required,
+  and other miscellaneous edits. (:issue:`2205`, :issue:`2248`, :pull:`2311`)
 * Substantiate definitions of solar/surface azimuth/zenith and aoi on the
   :ref:`nomenclature` page. (:issue:`2448`, :pull:`2503`)
 * Add a new reference page for the spectrum (:ref:`_spectrum_user_guide`) to the